The present invention relates to electrical circuits and more particularly to a control circuit for multiple battery systems with a capacity gauge on end equipment.
Portable electronic devices (e.g., notebook computers, cellular telephone, cordless telephones mobile data terminals, radio frequency portable communication devices, etc.) typically include a rechargeable battery that is charged by a recharging unit plugged into an AC power source, such as that found in conventional 115 VAC lines. Certain rechargeable batteries can be recharged by coupling the rechargeable battery to a DC voltage source (e.g., car adapter, plane adapter, airplane adapter, USB power bus). The recharging unit powers the portable device, while simultaneously charging the rechargeable battery. The portable device switches over to battery power upon removal of the portable device from the charging unit or the power source. Some portable electronic devices are provided with two or more batteries, so that the portable electronic device can be used for longer periods of time than is possible with a single battery.
In systems with multiple batteries, a switching network is required to allow selective charging and discharging of each battery pack, while maintaining isolation between battery packs, a battery charger and a load. The switching network is controlled by a control system or controller on the system end (e.g., portable electronic device), which also controls selective charging and discharging of each of the battery packs. Since rechargeable batteries have a limited lifespan, it is desirable to maximize the life of each battery during discharge cycles. This is accomplished by fully and efficiently charging and discharging the battery without causing temperature abuse and overcharging. Many known battery chargers do not have the capability to accurately determine the charge level and the total charge capacity of a battery and can overcharge the battery reducing its useful life. Most portable devices include removable or replaceable batteries. Therefore, maintaining charge history information at the system end is impractical since a batteries history can change when it is removed and used in another system or simply experiences normal discharge during periods of non-use. end is impractical since a batteries history can change when it is removed and used in another system or simply experiences normal discharge during periods of non-use.
One solution to this problem has been to provide a capacity or fuel gauge with every battery pack. The capacity or fuel gauge may employ a coulomb counter that maintains a coulomb charge count that is incremented or decremented during charging and discharging, respectively. The capacity gauge can also be employed to determine he battery voltage, temperature, discharge current out of the battery, charge current into the battery, and charge and discharge history of the battery. In the many high-end multiple battery systems, an architecture is used where a capacity gauge is built in the battery pack, and the selection circuit is built in the end equipment or system side. This architecture requires the use of one capacity gauge per pack, increasing battery pack cost. Additionally, this increases the size of the battery pack and the overall power consumed since the dedicated capacity gauge circuitry is powered by each battery even when a battery is not selected for providing power to the system.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates to a capacity gauge and control that measures a selected battery capacity of a plurality of batteries in a multiple battery system. The capacity gauge and a battery current sense resistor reside on the end equipment, while the battery pack contains minimal information associated with the battery pack. Control circuits and/or algorithms provide for proper pack selection and pack connection timing, as well as capacity gauge synchronization. The control circuits and/or algorithms can be integrated into the capacity gauge and/or be a separate device from the capacity gauge. Power up/down circuits provide power to the capacity gauge and/or control, and the battery pack selection devices at power up, power down and battery pack removal. The system is powered by a selected battery pack after the battery pack selection is executed, and the selected battery pack monitored by the capacity gauge.
In one aspect of the invention, a power sequencer component provides power to the capacity gauge and/or control during power up, power down and battery pack removal. The power sequencer component includes a voltage regulator (e.g., Low Dropout (LDO) regulator) that receives power from one of a highest pack voltage and a DC supply voltage during power up, power down and battery pack removal. The power sequencer can include diodes coupling the battery pack supplies that are configured in a diode xe2x80x9cORxe2x80x9d configuration to provide the highest voltage as the capacity gauge supply and/or control supply voltage. The voltage regulator provides a supply voltage to the capacity gauge and/or control, while a power sequencing algorithm is performed. The battery pack voltages are sampled and a desired battery pack is selected based on one or more parameters. The selected battery pack is then employed to power the capacity gauge and/or control during normal operation.
The following description and the annexed drawings set forth certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.